The present invention relates generally to communication networks, and, more particularly, to transitioning from DVMRP to BGMP for interdomain multicast routing over the internet multicast backbone.
In today""s information age, multicasting is gaining popularity as a technique for distributing information to groups of information consumers. Specifically, multicasting allows an information provider (referred to hereinafter as a xe2x80x9cmulticast sourcexe2x80x9d) to transmit a single unit of multicast information (referred to hereinafter as a xe2x80x9cmulticast packetxe2x80x9d) simultaneously to all information consumers (referred to hereinafter individually as a xe2x80x9cmulticast clientxe2x80x9d and collectively as xe2x80x9cmulticast clientsxe2x80x9d) in the multicast group, specifically by addressing the multicast packet to the multicast group using a multicast group address. The multicast clients monitor the communication network for multicast packets addressed to the multicast group.
One factor that is spurring the growth of multicast applications is the Internet Multicast Backbone (commonly referred to as the xe2x80x9cMbonexe2x80x9d). The MBone is a virtual network that is layered on top of sections of the physical Internet. The Mbone is composed of a number of multicast regions or domains (i.e., sections of the Internet that have been upgraded to support multicasting) that are interconnected over virtual point-to-point links (commonly referred to as xe2x80x9ctunnelsxe2x80x9d). Each tunnel interconnects a multicast border router in one multicast region to a multicast border router in another multicast region. The tunnels allow multicast traffic to pass from one multicast region to another multicast region over sections of the Internet that do not support multicasting.
In order to route multicast packets within a multicast region of the Mbone (i.e., intradomain multicast routing), the multicast routers within the multicast region exchange multicast routing information using a multicast routing protocol, such as Multicast Open Shortest-Path First (MOSPF), Distance Vector Multicast Routing Protocol (DVMRP), or Protocol-Independent Multicast (PIM). The multicast routers within a particular multicast region are required to run the same multicast routing protocol, although each multicast region may run a different multicast routing protocol.
In order to route multicast packets across multicast regions of the Mbone (i.e., interdomain multicast routing), the multicast border routers exchange multicast routing information using a separate multicast routing protocol. The predominant interdomain multicast routing protocol used by multicast border routers in the Mbone is DVMRP, which is a well-known protocol that is described in an Internet Draft of the Internet Engineering Task Force (IETF) entitled Distance Vector Multicast Routing Protocol, document draft-ietf-idmr-dvmrp-v3-08.txt (February 1999), hereby incorporated by reference in its entirety. However, the Mbone is migrating from DVMRP to the Border Gateway Multicast Protocol BGMP), which is a well-known protocol that is described in an Internet Draft of the Internet Engineering Task Force (IETF) entitled Border Gateway Multicast Protocol (BGMP): Protocol Specification, document draft-ietf-idmr-gum-04.txt (Nov. 17, 1998), hereby incorporated by reference in its entirety.
In order for BGMP to set up a multicast distribution tree across the Mbone, all multicast border routers in the Mbone would have to support BGMP. Therefore, in order to transition the Mbone from DVMRP to BGMP, it would be necessary to upgrade all multicast border routers to BGMP. Such upgrading of multicast border routers is unlikely within a relatively short period of time.
Instead, it would be preferable to upgrade individual multicast border routers to BGMP. Unfortunately, DVMRP and BGMP create different distribution trees, and therefore a multicast border router running BGMP will not interoperate with a multicast border router running DVMRP.
Thus, a need remains for a way upgrade a multicast border router from DVMRP to BGMP without requiring all multicast border routers to be upgraded to support BGMP.
In accordance with one aspect of the invention, a number of routers run an extended BGMP protocol in order to transition a piece of the Mbone DVMRP distribution tree to BGMP. The extended BGMP protocol allows the routers to create a regional BGMP tree that is rooted at router that is a member of the Mbone DVMRP distribution tree. The extended BGMP protocol ensures that no fowarding loops are created between the Mbone DVMRP distribution tree and the regional BGMP tree.